Use the Categories menu - The canonical approach: proven, reliable, proven reliable.
Use the Themes menu - For those who like to think about underlying themes and for those who like to be surprised. But be warned that my assignment of posts to themes is a little, umm, arbitrary, since many posts treat serious intellectual and emotional subjects with what I fondly think of as humour.
Use the Search function - With more than 730 key words, from patience (boo) to persistence (hurray), from Richard III (hurray) to Richard Feynman (hurray again), there's a good chance you'll find what you're looking for, and you're pretty much sure to find something.
Use the Archives drop-down menu - Useful for searching by date. Just in case.